Electric guitars generally come in two varieties—single coil and humbucker pickups. Single coil guitars typically consist of a single bar magnet wrapped within a coil or a plurality of permanent magnets wrapped within a coil that react to disturbances caused by the guitar's vibrating strings. These strings are made of a magnetically permeable material typically a ferromagnetic material (e.g., nickel, steel, and the like) and the magnetic lines of flux developed by the permanent magnets are intercepted by the vibrating strings. This causes variations in the field pattern and a varying current is caused to flow in the coils. The frequency of the current corresponds to (or tracks) the frequency of vibration of the strings.
Plucking the metal string causes the pickup to produce a low-powered electronic signal that corresponds to the string's vibrations. This signal is then amplified to a level capable of driving speakers. By producing sound waves, the speaker converts the electronic signal back into mechanical energy, mirroring the metal string's behavior.
The coils, as well as being influenced by vibration of the strings also are subjected to noise. Noise is produced by lighting, electric motors and appliances and other sources. This noise (or hum) adversely affects the quality of the sound reproduced by the pickups. The fundamental frequency of the electrical supply voltage, typically 50 Hz or 60 Hz, is converted into an audible hum in the amplifying equipment.
Leo Fender produced a single-coil pickup in the 1940s, the design of which is the basis for single-coil pickups made today. It picks up considerable hum along with the intended signals.
Seth Lover, working for the Gibson company in 1955, invented the humbucking pickup, also known as a “humbucker”, which employs two coils in opposite phase to each other (e.g., if the first coil is clockwise, the second is counter-clockwise) and with the magnetic field for each coil in opposite polarity to each other. This cancels the unwanted noise (hum) while preserving the signal. It was a commercial success and humbuckers remain popular today.
However, in spite of the hum, single-coil pickups also remain popular. This is because a single-coil pickup produces a different kind of tone quality from a humbucker. This tone is favored by numerous guitar players. Many attempts have been made to produce a pickup, which has the tone quality and size of a traditional single-coil pickup, with the noise-canceling attributes of a humbucker. To date, all of these solutions have employed a second coil. Some have been essentially scaled-down versions of the humbucker concept. Others have two coils stacked one on the other, either with or without shielding in-between. Others have employed a “dummy coil”, a coil set inside the pick guard or elsewhere where it is too far away from the strings to sense them; it is for noise-canceling only.
Any dual-coil design will necessarily have different properties from a single-coil design. If both coils sense the strings, two signals are combined, picking up different overtones than a single coil would. The impedance of the pickup is the result of the sum of the impedance of both coils. Impedance affects the amplitudes of the various frequencies in the signal transferred to the amplifier. This will affect tone regardless of whether or not the second coil is used to sense the strings.
Therefore, there is an unmet need in the market for a novel single-coil pickup that produces its unique tone quality while canceling out the hum.